The present invention relates to a digital radio transmission method for multi-applications, making it possible to accommodate a plurality of mobile terminals and provide a plurality of applications.
A personal Digital Cellular (PDC) and a Personal Handy-phone System (PHS) are currently available as digital radio communication systems. These systems adopt a Time Division Multiple Access (TDMA) method. This TDMA method operates as follows. A given channel is sectioned into time units called frames in the direction along time axis. Each frame is divided into time units called time slots. A base station assigns one of the time slots to a mobile station which is located within its service area and has requested use of a communication service. Then, the base station communicates with the mobile station within the time unit, called the time slot, that has been assigned to the mobile station every frame period. Generally, one time slot within one frame is assigned to one mobile station. As long as the communication service between the base station and the mobile station continues, that time slot is not assigned to any other mobile station to extend a communication service to another mobile station. This is because the TDMA was originally designed on a voice communication basis to provide a continuous data communication service. One time slot is considered sufficient to provide the communication channel capacity required for voice communication.
Meanwhile, a related technique has been disclosed in Japanese Patent Laid-Open Publication No. Hei 6-244791. In the radio communication method described in this publication, if a channel of poor radio communication quality is detected, a plurality of time slots, not one, are re-assigned to the mobile station using that channel, and the same signal data is encapsulated into these time slots and is transmitted to the mobile station. This method is designed to enhance data throughput at the receiving end by giving the receiving end the opportunity for receiving the same signal data multiple times.
As the area of multimedia has been entered, in the radio communications world as well, service-class-adaptive radio communication methods, such as Multimedia Mobile Access Communication (MMAC) high-speed radio access systems are currently being studied.